Report: US rogue nuke detection upgrades not worth the cost

In a review of nuclear detection technologies for border security, the …

The September 11 attacks caused a general reassessment of the major threats to the United States, and the general conclusion was that the primary nuclear risk has shifted from major nations to rogue states and terrorist cells. The splintered and hardline nature of these organizations eliminates both diplomacy and brinksmanship as effective deterrents. Further, rogue states and terrorist cells are most likely to deliver nuclear payloads by smuggling them into the country, so the US military's missile- and laser-based defense systems are effectively useless against these threats.

Today's primary defense is centered on preventing nuclear materials from entering the US. According to US Customs and Border Patrol, 98 percent of the shipping containers entering US maritime ports, 96 percent of trucks at Northern land border crossings, and 100 percent of those at Southern border crossings are scanned for nuclear materials using radiation portal monitors (RPMs). Congress recently asked the the National Academies of Sciences to review the efforts of the Domestic Nuclear Detection Office (part of the Department of Homeland Security) in the area of upgrading the nation's RPMs, and the NAS' interim findings were, well, unflattering.

In their most negative findings, the Academies determined that the added capabilities of next-generation radiation detectors are unlikely to justify their increased cost, and large-scale procurement should be delayed until new technologies can be developed.

As part of 2006's SAFE Act, the Domestic Nuclear Detection Office (DNDO) began accepting proposals for next-generation nuclear detection systems. Current-generation RPMs contain polyvinyl toluene (PVT) scintillators for gamma ray detection and helium-3 neutron detectors. PVT scintillators are the RPMs' primary drawback because they do not have spectroscopic capabilities, meaning they cannot determine the energies of incident radiation (and thus the identity of its source), only whether the radiation is present. Helium-3 neutron detectors are also not spectroscopic, but almost all neutron-producing nuclear materials are of security interest, so spectroscopy is unimportant for this application.

The next-generation radiation detectors are called advanced spectroscopic portals (ASPs) and, as their name suggests, they add gamma ray spectroscopy by replacing PVT with NaI or high-purity germanium (HPGe) scintillators. By adding spectroscopy, containers with naturally occurring radioactive materials or medical nuclear materials can be identified by their gamma ray signatures and allowed to pass without further inspection. Also, the added sensitivity of NaI and HPGe scintillators allows faster scanning.

To evaluate DNDO's progress in evaluating the performance of ASPs, the National Academies' report examined three areas: adequacy of the testing procedures, scientific rigor of the testing process, and a cost-benefit analysis of deploying the new systems. All three were found to be inadequate.

Early ASP testing examined scanning cargo containers under carefully controlled conditions, but the tests used the same radiation sources and load configurations used to calibrate the equipment—perhaps not the best way to test the systems. After an intervention by the National Academies of Science, subsequent testing used a wider array of radiation sources and container load configurations. These tests still sampled only a tiny fraction of the possible threat space, and need to be substantially increased before wide deployment of ASPs.

Because the sample space is so large, the Academies recommended using computer simulations to determine radiation signatures of nuclear material in a wide variety of configurations, including those hidden in loads that contain other non-threatening nuclear material. Both Sandia National Lab and Pacific Northwest National Lab have substantial experience in this area and could help improve testing procedures. Data from the simulations would provide input necessary to maximize the scientific value of real-world tests, and these tests would verify and enhance computer models.

In their most negative findings, the Academies determined that the added capabilities of APSs are unlikely to justify their increased cost, and large-scale procurement should be delayed until new technologies can be developed. ASPs would not significantly increase operational efficiencies at ports and borders, they are unlikely to enable manpower reductions, and decreased scan times are modest. Most importantly, there is no evidence that the new systems significantly decrease the chances of a false negative—that is, the chances that a container actually contains threatening nuclear material, but the system does not alert authorities.

Overall, the report offers a profoundly negative view of the ASP process. Not only was previous testing inadequate, but the goals of the program were structured so it was never likely to produce a substantial benefit. We've recently seen a number of examples of government science working effectively, but it has clearly missed the mark here.